1. Field of the Invention
The present invention concerns antigens and vaccines for infectious diseases and, more particularly, to antigens useful in the diagnosis and treatment of Human Immunodeficiency Virus.
2. Background of the Invention
Human Immunodeficiency Virus (HIV, also HTLV-III, LAV, ARV), a cytopathic lymphotropic retrovirus, is considered the probable causative agent of Acquired Immunodeficiency Syndrome (AIDS) in humans. [Gallo, et al., Science, 224:500 (1984); Popovic, et al., Science, 224:497 (1984); Sarngadharan, et al., Science, 224:506 (1984)]. The underlying disease state involves a tropism of HIV for the T4+ lymphocyte subset resulting in a selective depletion of the helper/inducer cells of the immune system, leaving the individual defenseless against a number of opportunistic infections.
There are currently more than 27,700 diagnosed cases of AIDS in the United States and the U.S. Public Health Service predicts that by the end of 1991 more than 179,000 persons will have the disease. It is believed that only 10 to 15 percent of those with clinical symptoms and 1 to 2 percent of those infected with HIV suffer the clinical syndrome of AIDS. The development of diagnostics and vaccines to HIV is the subject of intense medical research.
The nucleotide sequence of several independent viral isolates of HIV have been determined. [Ratner et al., Nature, 313(6000):227 (1985)]. The viral genome is reported to contain about 10 kilobases which encode four long open reading frames- gag, pol, sor, and env. The env open-reading frame of HIV, which consists of 863 amino acids, has been reported to encode a 160 kd precursor glycoprotein, designated gp160. This precursor glycoprotein is thought to be processed into a 120 kd exterior glycoprotein, designated gp120, and a 41 kd transmembrane protein, designated gp41. All three proteins have been found to react with AIDS patient sera. [Barin et al., Science, 228:1094 (1985); Sarngadharan et al., Science, 224:506 (1984)] Recombinant proteins derived from the env reading frame and other regions of the HIV genome are being studied as diagnostic and vaccine candidates. The following references are representative of this ongoing research.
Chang et al., Science, 228:93 (1985) discloses the expression in E. coli of open reading frame gene segments of HTLV-III. Cloned HTLV-III DNA was sheared into approximately 500-base-pair fragments and inserted into an "open reading frame" expression vector. The inserted DNA was expressed in E. coli transformants as fusion proteins which were immunoreactive with AIDS serum. Reactive fragments were derived from the open reading frame DNA segments corresponding to the gag and pol coding regions and also the open reading frame region env-lor located near the 3' end of the viral genome.
Crowl et al., Cell, 41:979 (1985) discloses HTLV-III env gene products synthesized in E. coli which are recognized by antibodies present in the sera of AIDS patients. A large segment of the env gene (1800 bp) was inserted into an expression vector. The inserted DNA was expressed in E. coli transformants as a recombinant protein containing 611 amino acids which encompassed both the extracellular and the membrane associated regions of the native protein. AIDS patient sera recognized the bacterially synthesized envelope protein in Western blot experiments.
Chang et al., Nature, 315:151 (1985) reports the production of a recombinant 15K peptide encoded by the 3' end of the viral pol gene. The peptide is described as strongly immunoreactive with with anti-HTLV-III antibodies present in sera from AIDS patients. Allan et al., Science, 230:810 (1985) discloses a HTLV-III/LAV 27,000 MW protein having a coding origin 3' to the env gene.
U.S. Pat. No. 4,520,113, issued to Gallo et al., discloses serological detection of antibodies to HTLV-III in sera of patients with AIDS and pre-AIDS conditions. HTLV-III isolated from AIDS patients and transmitted by cocultivation with an HT cell line is detected by antibodies from human sera taken from AIDS patients. The most prominant reactions are said to be directed to gp41, a 41,000 MW protein constituting the envelope antigen of the HTLV-III virus.